First-time donors provide 31% of all blood donations. Unfortunately, the majority of young and first-time donors do not return for a repeat donation, and only 2% of first-time donors under the age of 20 go on to become committed blood donors. Hence our blood supply is highly reliant on young donors who must constantly be replaced. In addition to enormous ongoing recruitment costs, failure to retain first-time donors has important health implications, as repeat blood donors are less likely to be deferred for poor health and to transmit infections such as HIV and hepatitis. Accordingly, for health, safety, and economic reasons there is a critical need for novel approaches to enhance the retention of new blood donors. The current application examines an innovative, theory-driven approach to retention by promoting intrinsic motivation to donate again among new blood donors. Self-determination theory (SDT) proposes that people are more likely to persist with behaviors that are internally versus externally motivated, and considerable research supports the notion that more internalized motivation is associated with better adherence in a variety of health contexts. Similar findings have also been reported in the blood donation context where measures of the extent to which a donor identity has been internalized are positively related to both donation intention and future donation behavior. Based on our prior work, we propose to test a multi-component intervention designed to enhance one, two, or all three of the fundamental human needs that contribute to internal motivation according to SDT (i.e., competence, autonomy, relatedness). Using a full factorial design, first-time donors will be randomly assigned to a control condition or an intervention that addresses one, two, or all three of the fundamental needs. Our primary outcome measure will be donation attempts in the one-year follow-up period. Additional outcome measures will include changes in donation competence, autonomy, and relatedness as well as key constructs from the Theory of Planned Behavior (attitude, subjective norm, perceived behavioral control, intention). Our primary aim is to determine whether the intervention conditions, alone and in combination, increase the likelihood of a donation attempt in the next year. Our second aim is to examine intervention-specific increases in competence, autonomy, and relatedness as potential mediators of enhanced donor retention. Finally, an exploratory aim will examine an integrative model of motivation that views autonomy as a mediating influence on the more proximal, situational-level determinants of behavior (i.e., attitude, subjective norm, perceived behavioral control, and intention). This project is significan, innovative, and timely as it develops a much-needed, new approach to first-time donor retention while examining specific, theory-driven intervention mechanisms that have never been tested in the donation context. This study will have an important public health impact by developing efficient interventions that can be widely disseminated to promote a safe and stable national blood supply.